The invention relates to a gear pump.
It is generally known that to convey and dose liquid, gear pumps are used in which the medium to be conveyed is transported by means of two gear wheels that engage in one another between a pump intake and a pump discharge. Through the plurality of conveyance units a very uniform conveyance volume can be set, such that gear pumps of this type are preferably used for the generation of uniform conveyance quantities such as the supplying of lacquer in a lacquer facility.
A gear pump of this type is known, for example, from DE 10 2005 059 563 A1. With the known gear pump, two gear wheels that engage in one another within a pump housing are rotatably supported and connected to a pump shaft. The pump shaft extends with a coupling end from the pump housing and can be coupled to a drive shaft of a motor. In the use of gear pumps of this type, having variable pressure loads at the discharge end or the intake end, or both ends, irregularities in the conveyance flow have been observed. Normally, the gear wheels contained in the pump housing are driven by means of torque transferred to the pump shaft. In the case that, as a result of pressure fluctuations, a reversal of the pressure differences between the pump intake and the pump discharge occurs, in addition to the torque of the pump shaft, additional pressure forces act on the tooth surfaces of the gear wheels in the direction of conveyance, such that, depending on the size of the pressure forces applied to the gear wheels, a change from a motorized drive to an internally induced drive can result. In other words, in this situation, the pressure drop from the inlet of the pump to the outlet drives the pump faster than the motor. This change in the load direction is transferred to the entire drive train. Due to the torsional play in the drive train, accelerations then occur, followed by slowing of the rotational speed of the gear wheels within a single rotation of the pump shaft. This occurrence results directly in an irregularity in the conveyance flow during a rotation of the pump shaft.